Neuroradiology Case of the Week

Case 8

Andrea Zynda-Weiss, MD and P-L Westesson, MD, PhD, DDS

Clinical Presentation: An 13-year-old patient with attention deficit disorder with new onset of seizures presented for imaging.

Radiographic Findings: The sagittal images show partial agenesis of the corpus callosum and a large arachnoid cyst. In the centrum semiovale bilaterally there are large bands of heterotopic gray matter. These show signal characteristics identical to gray matter on T1, T2 and FLAIR images.

Figure 1: Sagittal T1 weighted image demonstrates large midline arachnoid cyst and partial agenesis of the corpus callosum.

Figure 2: Axial T2 weighted image demonstrates bilateral bundles of gray matter in the centrum semiovale. The arachnoid cyst is present in the midline.

Figure 3A	Figure 3B

Diagnosis: Band Heterotopia

Discussion: Gray matter heterotopia are collections of nerve cells in abnormal locations secondary to arrest of radial migration of neurons. Heterotopia can be isolated or, as in this case, associated with other structural anomalies.
   Patients with heterotopic gray matter almost always present with seizure disorders [1–3]. Heterotopia is often divided into three groups: subependymal heterotopia, focal cortical heterotopia and band heterotopia.
   The current case does not fit any category exactly but is most consistent with band heterotopia. Patients with band heterotopia [4,5] often present with “double cortex”. The patient may present at any age although they are usually seen in childhood with developmental delay and variable severity of mixed seizure disorders [4,6,7]. Band heterotopia is more commonly seen in females (90%) and rarely seen in males [4,8].
   On imaging, band heterotopia appears as bands of gray matter situated between the lateral ventricle and cerebral cortex and separated from both by a layer of normal appearing white matter. Band heterotopia may be complete, surrounded by simple white matter, or partial. The frontal lobes, as in this patient, seem to be more frequently involved when it is partial.
   On PET imaging using FDG, band heterotopia has been found to have glucose uptake that is similar [9,10] or greater than [11] normal cortex. This finding contrasts the hypometabolism found in cortical dysplasias and in most epileptogenic foci.

References:

1. Raymond AA, Fish DR, Stevens JM, Sisodiya SM, Alsanjari N Shorvon SD. Subependymal heterotopia: a distinct neuronal migration disorder associated with epilepsy. J Neurol Neurosurg Psychiatry 1994;57:1195-1202.
2. Smith AS, Weinstein MA, Quencer RM et al. Association of heterotopic gray matter with seizures: MR imaging. Radiology 1988;168:195-198.
3. Barkovich AJ, Kjos BO. Gray matter hereotopias: MR characteristics and correlation with developmental and neurological manifestations. Radiology 1992;182:493-499.
4. Barkovich AJ, Guerrini R, Battaglia G et al. Band heterotopia: correlation of outcome with MR imaging parameters. Ann Neurol 1994;57:609-617.
5. Barkovich AJ, Jackson DE Jr, Boyer RS. Band heterotopias: a newly recognized neuronal migration anomaly. Radiology 1989;171:455-458.
6. Livingston JH, Aicardi J. Unusual MRI appearance of diffuse subcortical heterotopia or “double cortex” in two children. J Neurol Neurosurg Psychiatry 1990;53:617-620.
7. Palmini A, Andermann F, Aicardi J et al. Diffuse cortical dysplasia, or the “double cortex” syndrome: the clinical and epileptic spectrum in 10 patients. Neurology 1991;41:1656-1662.
8. Ono J, Mano T, Andermann E et al. Band heterotopia or double cortex in a male: bridging structures suggest abnormality of the radial glial guide system. Neurology 1997;48:1701-1703.
9. Falconer J, Wada J, Martin W, Li D. PET, CT, and MRI imaging of neuronal migration anomalies in epileptic patients. Can J Neurol Sci 1990;17:35-39.
10. Miura K, Watanabe K, Maeda N et al. MR imaging and positron emission tomography of band heterotopia. Brain Dev 1993;15:288-290.
11. De Volder AG, Gadisseux J-F, Michel CJ et al. Brain glucose utilization in band heterotopia: synaptic activity of “double cortex”. Pediatr Neurol 1994;11:290-294.